1. Field of the Invention
The present invention relates to an OTU frame data generating apparatus which generates and outputs OTU (OTU: Optical Channel Transport Unit) frame data for use in an optical transport network (OTN: Optical Transport Network), and in particular, to an OTU frame data generating apparatus and method using a technique in which multiframe structured data to be inserted into the overhead (OH: Overhead) portion thereof can be easily edited.
2. Description of the Related Art
In recent years, in addition to conventional various synchronous transmission systems SDH/SONET, PDH and ATM, or the like, an OTU frame structure for use in an optical transport network (OTN) in which various frames of these transmission systems are mapped and transmitted is regulated by ITU-T G.709.
The OTU frame is composed of an overhead portion (OH) of 4 row×16 column bytes and a payload portion of 4 row×4064 column bytes including an FEC (Forward error Correction) region for correcting errors as shown in FIG. 9.
As shown in FIG. 10, various information needed for transmitting OTU frame data are inserted in the overhead portion (OH).
In FIG. 10, the data of 6-byte length “FAS: Frame Alignment Signal” in the first row is information expressing the top of the frame or the like.
The data of 1-byte length “MFAS: Multiframe Alignment Signal” following the “FAS” is sequence number (0 to 255) information denoting what number frame of the multiframe this frame is, as shown in FIG. 9.
Namely, because the “MFAS” is to form a set of meaningful data by combining data of 256 frames (or the number of frames of ½ or ¼ thereof) of the multiframe structured data which will be described later, the “MFAS” is to denote what number frame among the 256 frames the frame is by the sequence number.
In other words, a set of meaningful data is completed every 256 frames (or the number of frames of ½ or ¼ thereof).
Among the respective data following this “MFAS”, respective “TTI: Transmitted Trace Identifier” data, which are denoted by applying oblique lines thereto and which include address information and the like, of “SM: Section Monitoring”, “TCM6”, “TCM5”, . . . , “TCM1” (Tandem Connection Monitoring) in the second row and the third row, and “PM: Path Monitoring” following the “TCM1”, “FTFL: Fault type and Fault Location reporting channel” data including field information “following TCM4” in the second row, and “PSI: Payload Structure Identifier” data including structural information in the fourth and fifteenth byte payload portion are respectively multiframe structured data of 1-byte length.
These multiframe structured data form a set of meaningful data by combining data of 256 frames (or the number of frames of ½ or ¼ thereof) as described above due to one byte being respectively allocated to each frame.
Further, the respective data other than the above-described data are respectively non-multiframe structured data which are respectively meaningful for each frame.
As these non-multiframe structured data, in addition to respective “BIP: Bit Interleaved Parity 8”s and respective “STATE”s of the above-described “SM”, and “TCM6”, “TCM5”, . . . , and “TCM1”, there are “GCC0 (General Communication Channel 0)”, “RES (Reserved for future international standardization)”, “JC (Justification Control)”, “TCM ACT (Activation)”, “EXP (Experimental)”, “GCC1”, “GCC2”, “APS (Automatic Protection Switching)/PCC (Protection Communication Channel)”, and “NJO (Negative Justification Opportunity)” data.
Note that “BEI (Backward Error Indication)” of 4 bits, “BDI (Backward Defect Indication)” and “IAE (Incoming Alignment Error” of respectively 1 bit, and “RES” of 2 bits are allocated to the above-described “STATE”s.
In this way, in particular, when transmitting equipment using OTU frame data having a frame structure in which multiframe structured data and non-multiframe structured data are mixed and inputted together into the overhead portion is constructed, it is necessary to test whether or not the information in the overhead portion is correctly recognized through each frame of the 256 frames (or the number of frames of ½ or ¼ thereof) from 0 to 255 which are needed for completing a set of meaningful data.
However, the conventional OTU frame data generating apparatus for this type of usage is constructed such that, with respect to each multiframe data information to be inserted into the overhead portion, only one set of data can be fixedly set through each multiframe of the 256 frames (or the number of frames of ½ or ¼ thereof) from 0 to 255 which are needed for completing a set of meaningful data.
Accordingly, in the prior art, because an apparatus for generating OTU frame data in which each multiframe data information to be inserted into the overhead portion can be arbitrarily set through each multiframe of the 256 frames (or the number of frames of ½ or ¼ thereof) from 0 to 255 which are needed for completing a set of meaningful frame data has been not realized, in particular, when transmitting equipment using OTU frame data having a frame structure in which multiframe structured data and non-multiframe structured data are mixed and inputted together into the overhead portion is constructed, there is the problem that it is impossible to test whether or not the information in the overhead portion is correctly recognized.
Therefore, in particular, when an OTU frame data generating apparatus for testing the transmitting equipment construction OTN is constructed, it has been strongly required that the OTU frame data generating apparatus which can generate OTU frame data in which each multiframe data information to be inserted into an overhead portion can be arbitrarily set through each multiframe of the 256 frames (or the number of frames of ½ or ¼ thereof) from 0 to 255 which are needed for completing a set of meaningful data is realized.